#calculate {
    width: 300px;
    height: 400px;
    border: 1px #32CD32 solid ;
    border-radius: 5px;
    background-color: #00CCFF;
}
input {
    width: 97%;
    border-radius: 7px;
    background-color: #40e0d0;
    height: 8%;
    align-content: center;
    margin: 4px;
    text-align: right;
    font-size: 20px;
}
#keyboard {
    width: 100%;
    border-radius: 5px;
    height: 85%;
}
table {
    width: 100%;
    height: 100%;
}
tr td {
    width: 25%;
    height: 17%;
    background-color: #33CCFF;
    border: 1px solid;
    border-radius: 7px;
    text-align: center;
}
tr td:hover {
    background-color: #3366FF;
    cursor: pointer;
}
tr td:visited {
    background-color: #333399;
}